Pre‑operative pain sensitivity : a prediction of post‑operative outcome in the obstetric population

Abstract

Context: Experimental assessments can determine pain threshold and tolerance, which mirror sensitivity to pain. This, in turn, influences the post‑operative experience. Aims: The study intended to evaluate whether the pre‑operative pressure and electrical pain tests can predict pain and opioid requirement following cesarean delivery. Settings and Design: Research was conducted on females scheduled for cesarean section at a tertiary care hospital of the state. Twenty women were enrolled, after obtaining written informed consent. Materials and Methods: Pain assessment was performed on the eve of cesarean sections using three devices: PainMatcher® determined electrical pain threshold while the algometers PainTest™ FPN100 (manual) and PainTest™ FPX 25 (digital) evaluated pressure pain threshold and tolerance. Post‑operative pain relief included intravenous morphine administered by patient‑controlled analgesia, diclofenac (100 mg, every 12 h, rectally, enforced) and paracetamol (1000 mg, every 4‑6 h, orally, on patient request). Pain scores were reported on numerical rating scales at specified time intervals. Statistical Analysis Used: Correlational and regression statistics were computed using IBM SPSS Statistics 21 software (IBM Corporation, USA). Results: A significant correlation was observed between morphine requirement and: (1) electrical pain threshold (r = –0.45, P = 0.025), (2) pressure pain threshold (r = –0.41 P = 0.036) and (3) pressure pain tolerance (r = –0.44, P = 0.026) measured by the digital algometer. The parsimonious regression model for morphine requirement consisted of electrical pain threshold (r2 = 0.20, P = 0.049). The dose of morphine consumed within 48 h of surgery decreases by 0.9 mg for every unit increment in electrical pain threshold. Conclusions: The predictive power of pain sensitivity assessments, particularly electrical pain threshold, may portend post‑cesarean outcomes, including opioid requirements.